Ocean Thermal Energy Conversion (OTEC) technology uses the existing temperature differential between ocean water at different depths to generate power. In many OTEC systems, an evaporator uses warm water drawn from near the ocean surface to heat a working fluid (e.g., ammonia), which is used to drive a turbine to generate electrical power. The working fluid is cooled by a condenser that uses cold water drawn from the deep ocean to absorb the heat from the working fluid. The cooled working fluid is then pumped back into the evaporator, and the cycle is repeated.
Many OTEC systems use a cold water pipe (CWP) to collect and transport the cold water from the deep ocean to the condenser, which may be located on an offshore platform or other structure at or near the ocean surface. A CWP may be 1000 meters in length or more and have a diameter of 4 meters or more. A CWP is typically assembled in a vertical orientation from a floating platform and extended into the ocean as the CWP is manufactured. Individual sections of CWP are typically manufactured on shore and are ferried out to the floating platform at significant expense. This is because the large cylindrical sections of CWP take up a large amount of space and are difficult to efficiently transport. Thus, it is desirable to reduce the cost associated with manufacturing CWPs.
In addition, during assembly, a CWP is rigidly coupled to a floating ocean platform and can take up to four months to assemble. CWPs must be designed to withstand the ocean environmental extremes that may occur during the manufacturing process. These environmental design conditions are selected based on the deployment time of individual CWPs. The driving ocean environmental conditions are wave height, wave period, wind speed, and ocean current, which may vary greatly based on seasonal and other conditions. After the CWP is operational and in place under the surface of the water however, the coupling of the CWP to the platform is no longer rigid, and the environmental forces the CWP will be subjected to are diminished. Thus, when building a CWP in a hurricane zone, for example, a longer build time requires the CWP to be built to withstand extreme forces that won't be encountered when in operation. Thus, it is also desirable to minimize build time for manufacturing a CWP.